Stretcher fiber and module

Abstract

A stretcher fiber has a core region, inner trench region, ring region, outer trench region, and outer cladding region. The fiber regions are structured to provide the stretcher fiber with a relationship between dispersion and wavelength, such that the second and third derivatives of the stretcher fiber's propagation constant with respect to angular frequency have a shape and wavelength range matching those of a selected compressor module.

The invention claimed is: 
     
       1. A stretcher fiber, comprising:
 a core region having a radius r 1 , a refractive index n 1 , and a positive refractive index difference Δn 1  with respect to an outer cladding region having an outer radius r 0  and a refractive index n 0 , where Δn 1  is equal to n 1 −n 0 , 
 an inner trench region surrounding the core region, the trench region having an outer radius r 2 , a refractive index n 2  less than n 0 , and a negative refractive index difference Δn 2  equal to n 2 −n 0 , 
 a ring region surrounding the trench region, the ring region having an outer radius r 3 , a refractive index n 3  greater than n 0 , and a positive refractive index difference Δn 3  equal to n 3  - n 0 , 
 an outer trench region surrounding the ring region, the outer trench region having an outer radius r 4 , a refractive index n 4  less than n 0 , and a negative refractive index difference Δn 4  equal to n 4 −n 0 , 
 the outer cladding region surrounding the outer trench region, 
 wherein the values of r 0 , r 1 , r 2 , r 3 , r 4 , Δn 1 , Δn 2 , Δn 3 , and Δn 4  are structured to provide the stretcher fiber with a relationship between dispersion and wavelength, wherein the stretcher fiber β 2 and β 3 /β 2 curves have a shape and wavelength range matching those of a selected compressor module, 
 wherein β 2  is the second derivative of the stretcher fiber's propagation constant β with respect to angular frequency ω: 
 
       
         
           
             
               
                 
                   β 
                   2 
                 
                 = 
                 
                   
                     
                       ⅆ 
                       2 
                     
                     ⁢ 
                     β 
                   
                   
                     ⅆ 
                     
                       ω 
                       2 
                     
                   
                 
               
               , 
             
           
         
       
       and
 wherein β 3  is the third derivative of the selected fiber's propagation constant β with respect to angular frequency ω: 
 
       
         
           
             
               
                 β 
                 3 
               
               = 
               
                 
                   
                     
                       ⅆ 
                       3 
                     
                     ⁢ 
                     β 
                   
                   
                     ⅆ 
                     
                       ω 
                       3 
                     
                   
                 
                 . 
               
             
           
         
       
     
     
       2. The stretcher fiber of  claim 1 , wherein the fiber has a polarization mode dispersion coefficient less than 0.2 ps/km −1/2 . 
     
     
       3. The stretcher fiber of  claim 1 , wherein the values of r 0 , r 1 , r 2 , r 3 , r 4 , Δn 1 , Δn 2 , Δn 3 , and Δn 4  are structured to provide the stretcher fiber with a relationship between dispersion and wavelength with a fourth derivative matching that of the selected compressor module. 
     
     
       4. The stretcher fiber of  claim 1 ,
 wherein the values of r 0 , r 1 , r 2 , r 3 , r 4 , Δn 1 , Δn 2 , Δn 3 , and Δn 4  are structured to cause the fiber to have a negative dispersion and to have a relative dispersion slope greater than 0.005 nm −1  at a specific wavelength within a selected operating wavelength band. 
 
     
     
       5. The stretcher fiber of  claim 1 , wherein the selected operating wavelength band is between 1000 and 1100 nm. 
     
     
       6. The stretcher fiber of  claim 5 , wherein the specific wavelength within the wavelength band is 1030 nm. 
     
     
       7. The stretcher fiber of  claim 5 , wherein the specific wavelength within the wavelength band is 1060 nm. 
     
     
       8. The stretcher fiber of  claim 1 . wherein the fiber has a cutoff wavelength below the selected operating wavelength band. 
     
     
       9. The stretcher fiber of  claim 8 , wherein the selected operating wavelength band is between 1000 and 1100 nm, and wherein the cutoff wavelength is 970 nm. 
     
     
       10. The stretcher fiber of  claim 1 , wherein the fiber is spliceable with a splice loss of less than 0.5 dB to a single-mode fiber having a cutoff wavelength below the operating wavelength hand. 
     
     
       11. The stretcher fiber of  claim 1 , wherein:
 r 0 =0.98 μm; 
 r 1 =3.94 μm; 
 r 2 =5.32 μm; 
 r 3 =7.08 μm; 
 r 4 =62.50 μm; 
 Δn 1 =21.9×10 −3 ; 
 Δn 2 =−8.9×10 −3 ; 
 Δn 3 =6.8×10 −3 ; and 
 Δn 4 =−1.0×10 −3 . 
 
     
     
       12. The stretcher fiber of  claim 11 , wherein the core, inner trench, ring, outer trench, and outer cladding are fabricated from SiO 2 , and wherein the core is doped with GeO 2 . 
     
     
       13. The stretcher fiber of  claim 12 , wherein the inner trench is doped with a mixture of GeO 2  and F. 
     
     
       14. The stretcher fiber of  claim 12 , wherein the inner trench is doped only with F. 
     
     
       15. The stretcher fiber of  claim 12 , wherein the ring is dope with a mixture of GeO 2  and F. 
     
     
       16. The stretcher fiber of  claim 12 , wherein the ring is doped only with GeO 2 . 
     
     
       17. The stretcher fiber of  claim 12 , wherein the outer trench is doped with a mixture of P 2 O 5  and F. 
     
     
       18. The stretcher fiber of  claim 17 , wherein the outer trench is additionally doped with GeO 2 . 
     
     
       19. The stretcher fiber of  claim 12 , wherein the outer trench is doped only with F. 
     
     
       20. A stretcher module for use in a pulse amplification system, the stretcher module comprising a unitary length of the stretcher fiber of  claim 1 .